Fix cancellation race condition in PipeStream cancellation callback (#65909)

Fix cancellation race condition in PipeStream cancellation callback (#65909)

* Fix cancellation race condition in PipeStream cancellation callback

The public PipeStream.SafePipeHandle property throws an exception if the handle has already been closed.  This code should have been using the internal InternalHandle property, which just gets the SafePipeHandle object if it exists.

* Update src/libraries/System.IO.Pipes/src/System/IO/Pipes/PipeStream.ValueTaskSource.cs

Co-authored-by: Adam Sitnik <adam.sitnik@gmail.com>
Co-authored-by: Adam Sitnik <adam.sitnik@gmail.com>